This invention relates to a method of forming green tires in a two-stage system and a tire building apparatus for carrying out this method. More particularly it relates to a transfer apparatus for transferring tire constituting members for use in the method and the tire building apparatus.
In forming green tires by a conventional method as disclosed in Japanese Patent Application Publication No. 62-35381, first an inner liner, a carcass and the like are attached to the circumference of a carcass band forming drum to form a cylindrical carcass band. The carcass band is then transferred from the carcass band forming drum to a green case forming drum by means of a band transfer. A pair of beads are then set onto the carcass band on the green case forming drum by means of a bead setting device. Thereafter, portions of the carcass band extending axially outwardly of the beads are turned up or folded about the beads by the use of turn-up device.
Sidewalls, rim cushions and the like are then supplied from a material supply apparatus to the carcass band thus formed so that these tire materials are attached to a circumference of the carcass band to form a green case. When such a green case is received by green case transfer from the green case forming drum, the green case transfer is raised and then moved toward the green tire forming drum so that the green case is transferred avoiding any interfering with the green case forming drum. Then the green case transfer is lowered immediately before the green tire forming drum, and thereafter the green case is delivered to the green tire forming drum.
On the other hand, the belt and the tread are successively attached onto a circumference of a belt-tread composite forming drum located between the green case forming drum and the green tire forming drum to form a toroidal belt-tread composite body. This composite body is transferred from the belt-tread composite forming drum to a position about the green case on the green tire forming drum by means of a belt-tread transfer. Then the green case inside the belt-tread composite body is expanded into a toroidal shape by action of the green tire forming drum so that the green case and the belt-tread composite body are firmly pressed to form a green tire.
With the tire building method and apparatus of the prior art as above described, however, only the carcass band forming operation is effected at the carcass band forming drum, while the setting of the beads, the turning-up (folding) of the carcass band and the attaching of the sidewalls are effected at the green case forming drum. Therefore, the cycle time of the green case forming drum is longer than that of carcass band forming drum. However, the carcass band forming drum and the green case forming drum are continuously operated so that the shorter cycle time of the carcass band forming drum is obliged to be prolonged to the longer cycle time of the green case forming drum. The result is that the operation efficiency is unavoidably lowered.
In the method and apparatus of the prior art as above described, moreover, the carcass band which is weak and soft and likely to be deformed is delivered from the carcass band forming drum to the band transfer and from it to the green case forming drum. Therefore, positional errors of the carcass band would occur each time it is delivered between the drums and the errors are apt to accumulate to larger errors. What is worse still, as the turning-up of the green case is effected in the state of the beads simply being pressed to the green case, the beads are often somewhat moved. From these facts, a coaxial relation or axial positions of the beads and the green case are shifted to detrimentally affect the uniformity of produced tires.
In order to transfer cylindrical tire constituting members from a first forming drum of a first building machine to a second forming drum of a second building machine coaxially extending in the same direction, a transfer apparatus has been known as disclosed in Japanese Patent Application Publication No. 62-35381 as above described. Such a transfer apparatus includes horizontal rails arranged extending above the first and second forming drums, a trolley supported by the rails movably between the first and second forming drums, and grasping means vertically movably supported by the trolley and grasping the cylindrical tire constituting member on its outside.
In transferring the tire constituting member by such an apparatus from the first forming drum to the second forming drum, after the tire constituting member on the first forming drum is grasped by means of the grasping means, the trolley and the grasping means are moved along the rails so that the tire constituting member is removed from the first forming drum. After the grasping means grasping the tire constituting member has been raised, the trolley, the grasping means and the tire constituting member are moved in unison along the rails to a position above the second forming drum. Thereafter, the tire constituting member and the grasping means are lowered until the tire constituting member and the second forming drum are brought into coaxial relation, and then the trolley is moved along the rail to deliver the tire constituting member to the second forming drum, thereby completing the transferring operation.
With such an apparatus for transferring tire constituting members, however, it is required to hang the rails from a ceiling or to support the rails from columns uprightly standing from a floor. Therefore, the apparatus tends to be large-sized and expensive as a whole.
Moreover, such rails generally interfere with beams of overhead traveling cranes provided for changing sizes of tires to be produced. Furthermore, tire constituting members and the grasping means must be raised and lowered every time transferring the members so that great energy is consumed for such undue raising and lowering operations.
In addition, although the time for the forming cycles of the first and second drums has been shortened by speed-up of the forming operation, the total time of all cycles of the apparatus becomes rather longer due to a long time required for transferring the tire constituting members grasped by only one grasping means from the first forming drum to the second forming drum.